The endothermic reactions, occurring in a process for steam hydrocarbon reforming can be described by the following reaction schemes: EQU CH.sub.4 +H.sub.2 O.revreaction.CO+3H.sub.2 (-.DELTA.H.degree.298=-49.3 kcal/mole) (1) EQU CH.sub.4 +2H.sub.2 O.revreaction.CO.sub.2 +4H.sub.2 (-.DELTA.H.degree.298=-39.4 kcal/mole) (2)
Corresponding reaction schemes can be established for steam reforming of hydrocarbons higher than methane. These steam reforming reactions occur in the process gas of hydrocarbons and steam being passed through a steam reforming catalyst at steam reforming conditions. The necessary heat for the endothermic reactions is usually supplied by combustion in a radiant furnace chamber in which the catalyst is arranged in vertical tubes extending through the furnace chamber.
It is known to utilize the heat of the product stream of reformed gas as a partial source of heat. Such a process is described in U.S. Pat. No. 4,079,017 according to which a first portion of the process gas is subjected to steam hydrocarbon reforming in a conventional radiant chamber, while a second portion of the process gas is subjected to steam reforming by indirect heat exchange with a product stream. The two portions of process gas is thereafter combined and subjected to further steam hydrocarbon reforming in a secondary reforming process in the presence of air to supply heat by internal combustion in the process gas. The product stream from the secondary reforming process serves as heat exchange medium for heating the second portion of process gas.
It is an object of the present invention to provide a process for steam hydrocarbon reforming in which heat from the product stream is utilized in a more economic way in combination with heat from a hot flue gas generated by combustion in a burner. It is another object of the present invention to provide a reactor for carrying out the process of the present invention.